Coronary artery disease generally refers to a build-up of cholesterol or plaque on the interior walls of the arteries of the heart. FIG. 1 is an illustration of an artery 10 having a layer of plaque 12 formed on the interior walls of the artery. This type of build-up of plaque 12 reduces the capacity of the affected arteries to carry blood thereby reducing the flow of blood through the arteries and the amount of blood delivered to the muscles the arteries supply. The plaque 12 can also weaken the walls of affected arteries. As shown in FIG. 2, a crack 14 may develop in the plaque 12 and cause a blood clot to form in an artery. Many heart attacks are caused by blood clots in the coronary arteries.
Currently, angiograms are widely used to diagnose coronary artery disease. An angiogram is an invasive procedure that usually requires cardiac catheterization wherein a catheter is inserted into the blood vessel being examined. FIG. 3 shows a prior art catheter 16 shown inserted into a patient's 18 blood vessel 20 starting near the patient's groin and extending through the blood vessel and into the patient's heart 22. This type of catheterization process is normally necessary before angiogram and subsequent angioplasty procedures are conducted. Normally, attached to the end of the catheter are suitable sensors. In some cases, the sensors are active sensor heads, which emit a radio frequency signal of about 1 MHz and project it towards the heart. These sensor heads are often positioned close to a patient's heart. The projected signal is reflected off the arteries of the heart and can be used to determine an approximate location of an occlusion. An angioplasty is done by inserting a cleaning tool through the artery to remove an occlusion. In some cases, both the angiogram and the angioplasty processes are agonizing for the patient and can be dangerous or even fatal.
When an obstruction occurs in an artery, the blood flow through the affected artery creates more turbulence than in an unobstructed artery. This turbulence normally generates high frequency sounds especially during the diastolic activity of the heart. High frequency bandwidth, spread spectrum signals that experience time and frequency scaling are difficult to decompose with narrow band analysis, such as Fourier transform, due to its sinusoidal kernel, which approximates the scaling effect with a Doppler shift. However, this type of high frequency signal represents an admissible kernel representation for using wavelet transform (WT) in appropriate signal processing algorithms. A wavelet transform analysis uses a more general analysis kernel, or mother wavelet.
In “Wavelet Applications in Medicine” by Akay et. al, IEEE Spectrum, 1997 pages 50-56, there are described techniques used in signal processing for detection of coronary artery disease in healthy and unhealthy patients. Although such technology has been proposed as providing a reliable measurement, the technology has not been fully developed and the multiplicity of acoustic sensors proposed has represented a substantial impediment to widespread usage.
Based on the foregoing, it is the general object of the present invention to provide an apparatus and method for diagnosing coronary artery disease that improves upon, or overcomes the problems and drawbacks associated with prior art methods and tools for diagnosing coronary artery disease.
Another object of the present invention is to provide a novel apparatus for detecting and determining the position of obstructions in a patient's coronary arteries.
A further object of the present invention is to provide a novel method of detecting the location of and the severity of obstructions in the coronary arteries.
It is also an object of the present invention to provide such an apparatus, which can be readily available, and that is reliable and relatively inexpensive.
Another object of the present invention is to provide an apparatus for detecting and determining the position of obstructions in a patient's coronary arteries, which may be constructed from readily available components at a reasonable cost to enable the widespread use thereof.
A still further object of the present invention is to provide a non-invasive method of determining the location and the severity of obstructions in the coronary arteries.